A glass panel including a pair of glass panes (hereinafter referred to as a “glass panel unit”) with a depressurized space between the pair of glass panes has been known in the art. The glass panel unit is also called an “insulated glazing”. The glass panel unit has excellent thermal insulation properties because the depressurized space reduces heat conduction. When a glass panel unit is manufactured, two glass panes to form a pair are bound together with a gap left between them, an inner space between the pair is evacuated, and the inner space is hermetically closed, thus forming a depressurized space there.
It has been proposed that spacers be used to maintain a sufficient thickness for the depressurized space of such a glass panel unit. The spacers are parts to be interposed between the two glass panes. The spacers are required to have some strength, and therefore, a metal is one of well-known materials for the spacers. Meanwhile, spacers made of a polymer have also been disclosed as in Patent Literature 1, for example.
When a polymer (a resin) is employed as a material for the spacers, light (an electromagnetic wave) such as ultraviolet radiation passing through glass and striking the spacers made of the resin would make the spacers easily degradable, which is not beneficial. Spacers easily degrade when included, in particular, in windows and the like directly exposed to exterior ultraviolet radiation. Degradation of the spacers leads to generation of gas from the resin, which increases pressure in the inner space, and thus, it may no longer be possible to securely maintain the depressurized space.